Die Direktreduktion von Feineisenerzen in Druckwirbelschichtreaktoren: Experimentelle Untersuchungen und morphologische Betrachtung zur Übertragung auf industrielle Prozesse

In industrial plants it was observed that the operating conditions in the prereduction stage have a significant effect on the final reduction degree. A laboratory scale, pressurized fluidized bed reactor was developed according to the concept of chemical similarity to perform experiments similar to industrial operating conditions. With this set-up, temperatures up to 900°C and operating pressures up to 10⁵ Pa absolute can be realized. Numerous experiments with H₂-rich reduction gas according to the FINMET^®-process and CO-rich reduction gas according to the FINEX^®-process were carried out. Temperature, residence time and gas composition were varied. The samples were analyzed and morphologically evaluated. The influence of the operating conditions in the prereduction stage on the final reduction degree was reproduced, studied and confirmed by morphological investigations.     

Humidity sensing performance of in-situ fabricated Cu/Cu2O/Cu2S-polymer nanocomposite via polyphenylene sulphide cyclisation route

We herein report the feasibility of novel polymer-inorganic solid state reaction route for simultaneous in situ generation of Cu2S and Cu nanostructures in polymer network. Polyphenylene Sulphide (PPS) which is engineering thermoplastic acts as chalcogen source as well as stabilizing matrix for the resultant nano products. Typical solid state reaction was accomplished by simply heating the physical admixtures of the two reactants i.e., copper acetate and PPS by varying molar ratios mainly 1:1, 1:5, 1:10, 1:15, 1:20 at the crystalline melting temperature (285 degrees C) of PPS. The synthesized products were characterized using various physicochemical characterization techniques like X-ray Diffractometry, Field emission Scanning Electron Microscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and X-ray photoelectron spectroscopy. The prima facie observations suggest occurrence of nanocrystalline Cu2S in case of product obtained with equimolar ratio, whereas remaining samples show mixture of Cu and Cu2O. The TEM analysis reveals nanoscale polydispersity (5-60 nm) and prevalence of mainly spherical morphological features in all the cases with occasional indications of plate like and cubical morphological features depending upon the molar ratio of the reactants. The humidity sensing characterization of these nanocomposites was also performed. The resistivity response with the level of humidity (20 to 70% RH) was compared for these nanocomposites. The linear response is obtained for all the samples. The sensitivity of 1:1 molar ratio sample was found to be maximum among all the samples.     

High-power all-fiber superfluorescent source with fused angle-polished side-pumping configuration

We report high-power operation of a broadband superfluorescent source with an all-fiber configuration. The superfluorescent source yields an amplified spontaneous emission (ASE) output of 43.2 and 25.1?W from both ends, respectively. The maximum combined ASE output is 68.3?W with a slope efficiency of 78.6%. The wavelength bandwidths (FWHM) of the counterpropagating and copropagating ASE output are 31.5 and 18.9?nm, respectively. The fused angle-polished side-pumping coupler is applied to set up the all-fiber configuration. Furthermore, the influence of reflectivity on the laser threshold of the ASE sources is studied theoretically. The experimental results agree with the theoretical analysis.     

邻里单元模式在生态社区规划中的运用

邻里单元模式是与TOD相适应的社区组织模式,其通过功能混合与步行距离的控制,从规划层面解决居民日常生活中对于公共服务的需求,从根本上减少居民的出行需求;同时,通过基本单元的自我增殖与TOD模式的土地利用方式相衔接,在实现土地价值最大化的同时,也使得居民与外界的交通更加便利,有利于促进复合、低碳和宜居的生态社区的形成。     

Electrochemically programmed release of biomolecules and nanoparticles

The controlled release of molecules or nanoparticle conjugates is an important tool for a wide range of applications in science and engineering. Here we demonstrate electrochemically programmed release of biomolecules and nanoparticles immobilized on patterned gold electrodes using the thiol-gold linkage. This technique exploits the reductive desorption of self-assembled monolayers and allows both spatially controlled release and regeneration of small molecules (e.g., drugs), biopolymers (e.g., peptides, proteins, DNA), protein assemblies (e.g., viruses), and nanoparticles (e.g., particle-DNA conjugates). Fluorescence microscopy is used to image the release of avidin and nanoparticles in phosphate-buffered saline and to determine the kinetics of desorption. We also demonstrate that the electrodes can be regenerated using the same conjugation scheme.     

数控机床故障维修实例分析

本文介绍了数控机床的几个故障现象及维修实例。     

Experimental Investigations of Abrasive Mixed Electro Discharge Diamond Grinding of Nimonic 80A

This paper presents a novel hybrid machining process (HMP) called abrasive mixed electro discharge diamond grinding (AMEDDG) in which abrasive powder is mixed in dielectric fluid to perform electro discharge diamond grinding (EDDG) action on a workpiece. In-house-fabricated AMEDDG setup was used to experimentally evaluate the performance of the process during the machining of Nimonic 80A. The effects of wheel speed, powder concentration, current, and pulse-on-time (POT) were investigated on the material removal rate (MRR). The surface morphological properties of the machined workpiece were investigated based on some quality surface indicators. The experimental results show that MRR of the workpiece was influenced by wheel speed, current, and powder concentration, and optimum MRR can be achieved at a wheel speed of 1400 RPM, a powder concentration of 4 g/L, a current of 10 A, and a POT of 26 µs.     

Development of an intravascular impedance catheter for detection of fatty lesions in arteries

Tissue angiotensin II (AngII) is increased in the infarcted rat heart, where it may have autocrine or paracrine properties that influence cellular protein synthesis and growth and therefore tissue repair. It was our hypothesis that treatment with an AT1 receptor antagonist would attenuate fibrous tissue formation after myocardial infarction (MI). To investigate a role for local AngII in the regulation of connective tissue formation during early and late wound healing that follows MI, this study was undertaken. Animals were randomized into two groups in which rats were or were not treated with the AT1 receptor antagonist losartan (10 mg x kg(-1) daily gavage). At 1 and 4 weeks after experimental MI was induced by coronary artery ligation, rat hearts were examined. Infarct size, infarct area, and collagen volume fraction at the site of infarction and in noninfarcted myocardium were determined by picrosirius red staining with videodensitometry. Quantitative in vitro autoradiography was used to detect AngII receptor binding density ((125)I-(Sar1,Ile8)AngII). Compared with an untreated MI control group, in losartan-treated rats we found (1) infarct size was comparable in both groups at weeks 1 and 4, (2) infarct area was comparable between groups at week 1 but was significantly reduced (p < 0.05) at week 4 in losartan-treated rats, (3) a detectable reduction in collagen volume fraction at the site of MI was not found at week 1 but was reduced (p < 0.05) at remote sites at week 4, (4) AngII receptor binding density was reduced (p < 0.05) by 50% at the site of MI at both weeks 1 and 4 in keeping with delivery of losartan to this site of injury. Thus AT1 receptor antagonism appears to influence late phase wound healing at and remote to the site of MI and suggests an association between AngII and the fibrogenic response that appears in the injured rat heart. Although still speculative, an attenuation in fibrosis after MI may account for less ventricular dysfunction and geometric remodeling of right and left ventricles and ventricular arrhythmias that have been observed in such rats treated with angiotensin converting enzyme inhibitor or AT1 receptor antagonist.     

Ultra-High Capacity and Cyclability of β-phase Ca0.14V2O5 as a Promising Cathode in Calcium-Ion Batteries

Crystalline water-free β-phase Ca_0.14V₂O₅ is reported for the first time as a viable cathode material for calcium-ion batteries (CIBs). In contrast to layered α-V₂O₅ and δ-Ca_xV₂O₅·nH₂O, which have limited capacity, the β-phase delivers a reversible capacity of ≈247 mAh g⁻¹, which corresponds to the insertion/extraction of Ca²⁺ between Ca_0.14V₂O₅ and Ca_1.0V₂O₅. The process of Ca²⁺ insertion process and the accompanying structural relaxation are theoretically and experimentally verified. The initial insertion of Ca²⁺ into Ca_0.14V₂O₅ causes a slight shift of oxygen atoms surrounding hepta-coordination sites, creating penta-coordinated sites that are then partially filled up to Ca_0.33V₂O₅. Further insertion occurs through the stepwise occupation of up to 50% of neighboring hexa- and tetra-coordination sites to form Ca_0.67V₂O₅ and Ca_1.0V₂O₅, respectively. The rearrangement of oxygen atoms in Ca_0.14V₂O₅ also minimizes dimensional changes, leading to high cyclic stability during repeated charge/discharge cycles. The remarkable electrochemical performance of full cells containing a Ca_0.14V₂O₅ cathode and a K metal anode in Ca²⁺/K⁺ hybrid electrolytes, is also demonstrated, thanks to the inertness of K⁺ insertion into Ca_0.14V₂O₅ and the absence of calcium plating/stripping. The cyclic stability and high capacity of Ca_0.14V₂O₅ is not compromised in hybrid electrolytes, making it a viable CIB cathode.     

Solvent Mediated Nanoscale Quasi-Periodic Chirality Reversal in Self-Assembled Molecular Networks Featuring Mirror Twin Boundaries

Grain boundaries in polycrystals have a prominent impact on the properties of a material, therefore stimulating the research on grain boundary engineering. Structure determination of grain boundaries of molecule-based polycrystals with submolecular resolution remains elusive. Reducing the complexity to monolayers has the potential to simplify grain boundary engineering and may offer real-space imaging with submolecular resolution using scanning tunneling microscopy (STM). Herein, the authors report the observation of quasi-periodic nanoscale chirality switching in self-assembled molecular networks, in combination with twinning, as revealed by STM at the liquid/solid interface. The width of the chiral domain structure peaks at 12–19 nm. Adjacent domains having opposite chirality are connected continuously through interdigitated alkoxy chains forming a 1D defect-free domain border, reflecting a mirror twin boundary. Solvent co-adsorption and the inherent conformational adaptability of the alkoxy chains turn out to be crucial factors in shaping grain boundaries. Moreover, the epitaxial interaction with the substrate plays a role in the nanoscale chirality reversal as well.